Growth Hormone Releasing Peptide-6
Also Known AsGHRP-6 · His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 · SKF-110679
Developed by Cyril Y. Bowers at Tulane University as one of the first synthetic hexapeptide growth hormone secretagogues. Identified through systematic screening of enkephalin-derived peptides for GH-releasing activity, leading to the discovery that the ghrelin receptor (GHS-R1a) — later identified in 1996 — was the endogenous target.
His-D-Trp-Ala-Trp-D-Phe-Lys-NH2How GHRP-6 Works
GHS-R1a (Ghrelin Receptor) Agonism
Activates GHS-R1a on anterior pituitary somatotrophs via the Gq/11-PLC-IP3-Ca2+ signaling cascade, triggering growth hormone vesicle exocytosis. GHRP-6 is a potent but non-selective GHS-R1a agonist — it also engages the receptor at hypothalamic and peripheral sites, producing broader hormonal effects compared to ipamorelin.
Hypothalamic GHRH Stimulation
In addition to direct pituitary action, GHRP-6 stimulates GHRH release from arcuate nucleus neurons and suppresses somatostatin release from periventricular neurons. This dual hypothalamic action amplifies the GH response beyond what direct pituitary stimulation alone would achieve.
Appetite & Ghrelin Signaling
GHRP-6 mimics ghrelin's orexigenic (appetite-stimulating) effects by activating GHS-R1a in the hypothalamic arcuate nucleus, stimulating NPY/AgRP neurons. This produces notable increases in appetite and food intake — a pharmacological effect not seen with more selective secretagogues like ipamorelin.
ACTH-Cortisol & Prolactin Stimulation
At GH-effective doses, GHRP-6 produces measurable increases in ACTH, cortisol, and prolactin. These off-target effects are mediated by GHS-R1a populations on corticotrophs and lactotrophs and distinguish GHRP-6 from the more selective ipamorelin.
Published Research
Growth Hormone Physiology
StrongGHRP-6 was instrumental in establishing the existence of the GHS receptor system (later identified as GHS-R1a / ghrelin receptor). Extensive pharmacological characterization in humans and animals demonstrated dose-dependent GH release, synergy with GHRH, and desensitization kinetics. This body of work laid the foundation for all subsequent GH secretagogue research.
Cardioprotection
ModeratePreclinical research demonstrates cardioprotective effects in ischemia-reperfusion models, mediated partly through GHS-R1a expressed on cardiomyocytes. GHRP-6 reduces infarct size and prevents post-ischemic ventricular remodeling in rat models, with effects attributed to anti-apoptotic signaling (PI3K/Akt) and reduced inflammatory infiltration.
Hepatic Fibrosis & Cytoprotection
PreclinicalStudies in liver fibrosis models (CCl4-induced, bile duct ligation) demonstrate anti-fibrotic and cytoprotective effects. GHRP-6 reduces hepatic stellate cell activation, collagen deposition, and inflammatory cytokine expression. Effects appear partially independent of GH/IGF-1 axis, suggesting direct GHS-R1a-mediated tissue protection.
GH Deficiency Diagnosis
StrongGHRP-6 is used clinically as a provocative test agent for growth hormone deficiency diagnosis. Combined GHRH + GHRP-6 testing provides high sensitivity and specificity for GHD diagnosis, and is recognized in endocrine clinical guidelines as a standard stimulation protocol.
Safety Profile
GHRP-6 has extensive clinical pharmacology data from diagnostic and research use. Known effects include transient cortisol and prolactin elevation, significant appetite stimulation, and facial flushing. These are dose-dependent and generally resolve within 1-2 hours. Unlike ipamorelin, the cortisol and appetite effects represent meaningful pharmacological actions to consider in research design. Well-tolerated as a single-dose diagnostic agent.
Handling & Storage
Reconstitute with bacteriostatic water. Store lyophilized powder at -20°C. Reconstituted solution at 2-8°C, use within 21 days. Standard peptide handling — protect from heat and repeated freeze-thaw cycles.
Peer-Reviewed Literature
- 1
On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone
Bowers CY, Momany FA, Reynolds GA, Hong A.
- 2
Blocked growth hormone-releasing peptide (GHRP-6)-induced GH secretion and absence of the synergic action of GHRP-6 plus GH-releasing hormone in patients with hypothalamopituitary disconnection: evidence that GHRP-6 main action is exerted at the hypothalamic level
Popovic V, Damjanovic S, Micic D, et al.
- 3
Growth-hormone-releasing peptide 6 (GHRP6) prevents oxidant cytotoxicity and reduces myocardial necrosis in a model of acute myocardial infarction
Berlanga J, Cibrian D, Guillen I, et al.
- 4
Comparisons among old and new provocative tests of GH secretion in 178 normal adults
Aimaretti G, Baffoni C, DiVito L, et al.
GHRP-6 FAQ
What is GHRP-6?
GHRP-6 (Growth Hormone Releasing Peptide-6) is a synthetic hexapeptide that stimulates growth hormone release by activating the GHS-R1a (ghrelin) receptor. Developed in the 1980s by Cyril Bowers, it was one of the first synthetic GH secretagogues and was instrumental in the discovery of the ghrelin receptor system.
How does GHRP-6 differ from Ipamorelin?
Both activate GHS-R1a, but GHRP-6 is non-selective: it also stimulates ACTH, cortisol, prolactin release, and produces significant appetite stimulation through hypothalamic ghrelin signaling. Ipamorelin produces selective GH release without these off-target hormonal effects. GHRP-6 may produce a stronger total GH response but with a broader hormonal footprint.
Does GHRP-6 increase appetite?
Yes, significantly. GHRP-6 mimics ghrelin's orexigenic action in the hypothalamus by activating NPY/AgRP neurons in the arcuate nucleus. This is a well-documented pharmacological effect, not a side effect — it is the same mechanism by which endogenous ghrelin stimulates hunger.
Is GHRP-6 used in clinical settings?
Yes. The combined GHRH + GHRP-6 stimulation test is an established provocative test for diagnosing growth hormone deficiency in clinical endocrinology. It is recognized in international guidelines for its sensitivity and specificity in GHD assessment.
How should GHRP-6 be stored?
Store lyophilized powder at -20°C. Reconstitute with bacteriostatic water; store reconstituted solution at 2-8°C and use within 21 days.
GHRP-6 Products
All compounds 99%+ purity, verified by Janoshik Analytical. GMP-manufactured lyophilized powder.
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Disclaimer: This monograph is provided for educational and research purposes only. G26x Peptides products are sold exclusively as research chemicals. They are not intended for human consumption, therapeutic use, or as dietary supplements. All research should be conducted in compliance with applicable laws and institutional review board protocols. Information presented here is sourced from published peer-reviewed literature and does not constitute medical advice.